The present invention is particularly directed toward composite light-polarizing synthetic plastic ethical lenses of the type disclosed in application Ser. No. 41,504, now abandoned, also assigned to Polaroid Corporation. Such lenses are generally adapted to be utilized in providing substantially any given ophthalmic lens prescription to accommodate the eyes of a prospective user and facilitate a correction to such user's vision, while at the same time providing to such user the benefits which may only be achieved by employing a light-polarizing material.
It will be apparent that many advantages may be achieved by utilizing a tough, optical quality plastic material for ophthalmic lenses in lieu of glass. Plastics are more highly resistant to fracture glass, do not require extremely high temperatures to produce a desired lens, and do not generally require the expensive grinding and polishing operations which must be carried out, in most cases, before a glass lens is completed. Until the advent of modern transparent optical quality synthetic plastic materials, it was highly undesirable to form lenses from synthetic plastics since most of the available plastics were soft and therefore susceptible to severe abrasion. In addition, in those instances where tough, thermosetting resins were utilized for lens manufacture, such resins were difficult to handle in the thicknesses required for ophthalmic lenses. Until the development of the lenses described in the aforenoted application, people requiring corrective lenses to restore and/or aid their vision were denied the benefits of light-polarizing lenses which were made entirely of synthetic plastic materials. The few light-polarizing ethical lenses available comprised glass elements between a light-polarizing member was interposed. However, this obviously did not eliminate any of the problems inherent in glass lenses and, due to the difficulties encountered in the manufacture of such lenses and the extremely high incidence of rejects, such lenses were inordinately expensive.
As has been claimed in the above-denoted application, the method of manufacturing synthetic plastic ophthalmic lenses generally comprises the injection of a synthetic plastic monomeric material immediately adjacent each side of a light-polarizing element secured into a mold. The respective curvatures of the surfaces of the ultimately produced lens are, of course, governed by the shapes of the surfaces of the mold elements adjacent each respective surface of the light-polarizing element and offset therefrom a predetermined distance. Since, as will be appreciated from the discussion hereinbelow, plastic ophthalmic lenses are generally ground to a given prescription by grinding only the rear of concave surface of the lens, the light-polarizing element should be offset toward the convex side of the lens as much as possible thereby providing a substantially thicker concave in situ polymerized component than the convex in situ polymerized component. According to the disclosure in application Ser. No. 249,550, filed May 2, 1972, also assigned to Polaroid Corporation, this may be facilitated by securing into a resilient mold component a light-polarizing element which has been provided with projections about its periphery to provide such predetermined distance between at least one face of the light-polarizing element and its complementary mold component, although the same result may be accomplished by providing a shim of a predetermined thickness between the front mold and the polarizer.
It has been found that, in accordance with the method for manufacturing synthetic plastic composite light-polarizing lenses disclosed and claimed in above-denoted application Ser. No. 41,504, under certain circumstances catalyst utilized with monomeric materials required to form outer lens components of the lenses disclosed therein often migrates from the monomeric materials in which they are contained into the light-polarizing element which forms an integral component of the ultimate lens thereby deleteriously affecting the light-polarizing element by bleaching dyes comprising the element. In addition, plasticizer components of the light-polarizing element were sometimes found to migrate therefrom into polymerizing monomer which causes the formation of a "soft" polymeric material generally containing striations and haze; and monomer sometimes migrated into the light-polarizing element and caused it to deform and buckle. By the instant invention, a combination tiecoat-barrier layer is provided with obviates the migration effect of catalysts, monomeric materials, and plasticizers which are employed in forming the composite lenses of the present invention and insures adequate adhesion between the components of the composite structure.